For many years grapevines have been supported from various combinations of grape stakes and trellis wires that are arranged to permit lateral branching of the grapevine canes from the central vine root stock. More recently, however, it has been discovered that greater fruit production can be achieved if the grapevine foliage is vertically trellised, i.e., encouraged to grow in a vertical plane generally aligned with the grapevine trunk.
Support of grapevine foliage and fruit in a vertical trellising system has been previously accomplished by using pairs of foliage support wires that are positioned on either side of relatively wide grape stakes. Thus, for example, four inch wide wooden grape stakes can be positioned at about 25 foot intervals. Pairs of nails are driven into opposite sides of each stake at several selected heights so that pairs of movable trellis wires can be lifted up from the base of the stake and supported on adjacent pairs of nails. Most typically, at least two pairs of movable trellis wires are mounted and extend along the stakes. The system usually further includes permanent wires to support the canes or the Cordon intermediate and below the movable trellis wires in a position to support the fruit. In some systems, a third set of trellis wires is located below the first two pairs so as to enable training of foliage for growth in a plane both above and below the primary cane branches from the trunk.
In most of the vertical trellising systems, the nails are provided at more than two heights so that the movable trellis wires can be adjusted over the growing season by simply lifting them from one pair of nails to another. Typically, the pairs of trellis wire support nails are positioned at about 8 to 16 inch intervals above and below the permanent Cordon or fruiting wires and about that interval from each other. Depending upon the variety of the grapevines involved, the permanent wires are located at about 21/2 to 31/2 feet above the ground.
For many years, however, the vast majority of vineyard owners have employed horizontal trellising systems. Accordingly, many grape growers have grape stake and trellis systems which are already installed and are set up for horizontal branching of the grapevine foliage. Conversion of such a horizontal trellising system to a vertical trellising system is not difficult, however, if the grower has wooden grape stakes. Vertical trellising can be accomplished by removing lateral arms from the grape stakes and by adding trellis wire support nails to the sides of the grape stakes.
A complicating factor in the conversion from horizontal trellising to vertical trellising is that there has been a strong movement by growers toward the use of metal grape stakes instead of wooden stakes. Metal stakes have had certain performance advantages over wooden stakes and at least arguable structural and useful life advantages with respect to wooden stakes.
Conversion of metal grape stake horizontal trellising systems to vertical trellising systems is, however, much more difficult than when one tries to convert a wooden grape stake system. While some metal grape stakes are not high strength steel stakes, the addition of a trellis wire support structure to steel grape stakes in the field can be quite time consuming and expensive. Thus, the cost of converting a vineyard having metal grape stakes to vertical trellising can essentially offset the increased production that vertical trellising brings.
Accordingly, it is an object of the present invention to provide a trellis wire support apparatus and method which is suitable for use in converting metal grape stakes to vertical trellising of grapevines.
Another object of the present invention is to provide a trellis wire support clip which may be easily added in the field to previously installed metal grape stakes.
Still a further object of the present invention is to provide a trellis wire support clip for a vertical trellising system which is durable, compact, and has a minimum number of components.
Still a further object of the present invention is to provide a trellis wire support system in which trellis wires can be removably mounted to and lifted from the support clip by machine and yet will not be lifted off of the support clip by the wind.
Still another object of the present invention is to provide a method for supporting trellis wires for vertical trellising of grapevines from metal grape stakes.
Still a further object of the present invention is to provide a trellis wire support clip which can withstand substantial loading.
A further object of the present invention is to provide a trellis wire support clip having a structure which can be adapted for use with commonly employed metal grape stakes.
The trellis wire support clip and method of the present invention have other objects and features of advantage which will become apparent from and are set forth in more detail in the Best Mode Of Carrying Out The Invention and the accompanying drawing.